Method of post-twinning dual solid foamed insulation

Abstract

The present invention relates to a method for making wire insulation that comprises the steps of providing a solid insulative material; adding a chemical foaming agent to at least one section of the solid insulative material; extruding the solid insulative material over at least one wire to create an insulated wire; and heating the insulated wire after extruding the solid insulative material and activating the chemical foaming agent in the at least one section of the solid insulative material to create at least one foamed section in the solid insulative material.

What is claimed is: 
     
       1. A method for making wire insulation, comprising the steps of:
 providing a solid insulative material; 
 adding a chemical foaming agent to at least one section of the solid insulative material; 
 extruding the solid insulative material over at least one wire to create an insulated wire; 
 twisting the insulated wire prior to heating the insulated wire; and 
 heating the insulated wire after extruding the solid insulative material and after twisting the insulated wire, and activating the chemical foaming agent in the at least one section of the solid insulative material to create at least one foamed section in the solid insulative material. 
 
     
     
       2. A method according to  claim 1 , further comprising the step of:
 adding the chemical foaming agent to a plurality of sections of the solid insulative material to create a plurality of foamed sections in the solid insulative material after extruding the solid insulative material. 
 
     
     
       3. A method according to  claim 2 , wherein
 the plurality of foamed sections make up about 80% of the insulative material. 
 
     
     
       4. A method according to  claim 1 , further comprising the step of:
 adding the chemical foaming agent to substantially all of the solid insulative material. 
 
     
     
       5. A method according to  claim 1 , further comprising the step of:
 adding an ink to a select region of the solid insulative material to prevent the select region from foaming when heating the insulated wire. 
 
     
     
       6. A method according to  claim 5 , wherein
 the select region provides identification of the wire. 
 
     
     
       7. A method according to  claim 5 , wherein
 the ink is one of a free radical catalyst, organic per-compounds, peroxides, or azocatayst. 
 
     
     
       8. A method according to  claim 1 , further comprising the step of
 adjusting the amount of chemical foaming agent in the insulative material to tune the electrical properties of the wire. 
 
     
     
       9. A method according to  claim 1 , further comprising the step of:
 creating a groove in an outer surface of the solid insulative material after activating the chemical foaming agent. 
 
     
     
       10. A method according to  claim 1 , wherein
 the solid insulative material is one of a FEP, HDPE, MFA, Halar, PVC, or fluoropolymer. 
 
     
     
       11. A method according to  claim 1 , wherein
 the chemical foaming agent is one of substituted hyrdrazides, substituted azo compounds, substituted nitroso compounds, azodicarbonamide, sulfohydrazide, or sodium bicarbonate. 
 
     
     
       12. A method according to  claim 1 , further comprising the step of
 applying the chemical foaming agent as a coating over the solid insulative material. 
 
     
     
       13. A method for making wire insulation, comprising the steps of:
 providing a solid insulative material; 
 adding a chemical foaming agent to at least one section of the solid insulative material; 
 extruding the solid insulative material over first and second wires to create first and second insulated wires; 
 twinning the first and second insulated wires in a twisted wire pair prior to heating the insulated wires; and 
 heating the first and second insulated wires after extruding the solid insulative material over the first and second wires and after twinning the first and second insulated wires, and activating the chemical foaming agent in the at least one section of the solid insulative material to create at least one foamed section in the solid insulative material in at least one of the first and second insulated wires. 
 
     
     
       14. A method according to  claim 13 , further comprising the step of:
 twisting each of the first and second insulated wires. 
 
     
     
       15. A method according to  claim 13 , further comprising the step of:
 adding the chemical foaming agent to a plurality of sections of the solid insulated material to create a plurality of foamed sections in the solid insulative material of at least one of the first and second insulated wires. 
 
     
     
       16. A method according to  claim 15 , wherein
 the plurality of foamed sections make up about 80% of the insulative material. 
 
     
     
       17. A method according to  claim 13 , further comprising the step of:
 adding the chemical foaming agent to substantially all of the solid insulative material. 
 
     
     
       18. A method according to  claim 13 , further comprising the step of:
 adding an ink to a select region of the solid insulative material to prevent the select region from foaming. 
 
     
     
       19. A method according to  claim 13 , further comprising the step of:
 adjusting the amount of chemical foaming agent in the insulation to tune the electrical properties of the wire. 
 
     
     
       20. A method according to  claim 13 , wherein
 the solid insulative material is one of a FEP, HDPE, MFA, Halar, PVC, or fluropolymer. 
 
     
     
       21. A method according to  claim 13 , further comprising the step of
 creating a groove in an outer surface of the solid insulative material after activating the chemical foaming agent. 
 
     
     
       22. A method according to  claim 13 , further comprising the step of
 applying the chemical foaming agent as a coating over the solid insulative material.